Water and other volatile chemicals have been found inside these spherules of lunar glass.

Credit: NASA

Water and other volatile chemicals have been found inside these spherules of lunar glass.

Credit: NASA

In a finding that counters the prevailing wisdom that the moon has always been dry as a bone, a new study shows that small spheres of lunar volcanic glass contain water. Alberto E. Saal of Brown University and colleagues studied small glass spherules retrieved from the moon's surface by Apollo astronauts in the 1960s and '70s. Although scientists have analyzed the beads numerous times over the past 40 years, they've never found any trace of volatile elements. But now, using secondary ion mass spectrometry—an ultrasensitive technique that improves detection limits by over an order of magnitude—Saal's group identified water and other volatiles, such as fluorine, inside the spherules (Nature2008, 454, 192). They ruled out contamination from other sources. The beads most likely were formed during volcanic eruptions that occurred during the moon's early history, 3.5 billion years ago. The finding is all the more intriguing, the scientists say, given that recent orbiting spacecrafts have spotted possible water ice inside craters at the moon's poles.